Copper(I)-catalyzed Cyclization Reactions of Ethyl (E)-α-Ethynyl-β-Aryl-α,β-Unsaturated Esters with N-Sulfonyl Azides: Synthesis of 1-Aminonaphthalene, 3-Aminobenzofuran, and 3-Aminothiobenzofuran Derivatives

Article abstract of DOI:10.1002/bkcs.11755

A synthetic method for ethyl 4-(alkyl or arylsulfonamido)-2-naphthoates from ethyl (E)-α-ethynyl-β-aryl-α,β-unsaturated esters (1) and N-sulfonyl azides (2) in the presence of 2,6-lutidine in THF at 60 °C for 3 h was developed in one step, in which a copp

Full text of DOI:10.1002/bkcs.11755

Article
DOI: 10.1002/bkcs.11755
BULLETIN OF THE
J.-Y. Son et al.
KOREAN CHEMICAL SOCIETY
Copper(I)-catalyzed Cyclization Reactions of Ethyl (E)-α-Ethynyl-
β-Aryl-α,β-Unsaturated Esters with N-Sulfonyl Azides: Synthesis of
1-Aminonaphthalene, 3-Aminobenzofuran, and
3-Aminothiobenzofuran Derivatives
*
Jeong-Yu Son, Gi Uk Han, Gi Hoon Ko, Chanyoung Maeng, Seohyun Shin, and Phil Ho Lee
Department of Chemistry, Kangwon National University, Chuncheon 24341, Republic of Korea.
*E-mail: phlee@kangwon.ac.kr
Received March 5, 2019, Accepted April 17, 2019
A synthetic method for ethyl 4-(alkyl or arylsulfonamido)-2-naphthoates from ethyl (E)-α-ethynyl-β-aryl-
ꢀ
α,β-unsaturated esters (1) and N-sulfonyl azides (2) in the presence of 2,6-lutidine in THF at 60 C for
3 h was developed in one step, in which a copper(I)-catalyzed 1,3-dipolar cycloaddition, ketenimine for-
mation, and 6π-electrocyclization followed by [1,3]-H shift tandem reaction took place. This method
enabled efficient synthesis of a wide range of 1-aminonaphthalene and 3-aminobenzofuran and
3-aminobenzothiophene derivatives with the release of molecular nitrogen.
Keywords: Aminonaphthalene, Dipolar cycloaddition, Ketenimine, Cyclization, Copper
Introduction
some functionalized 1-halonaphthalene derivatives are not
commercially available.
The structural motif of 1-aminonaphthalenes exists broadly
in biologically active compounds used as a protein kinase
and angiogenesis inhibitors for the treatment of cancer,1
Mcl-1 inhibitors,2 p38 inhibitors,3 and BRAF inhibitors
(Figure 1).4 Accordingly, development of efficient synthetic
method for functionalized 1-aminonaphthalene derivatives
is of great importance.
Normally, functionalized 1-aminonaphthalene derivatives
were prepared by nucleophilic aromatic substitution reac-
tion of 1-halonaphthalene derivatives with primary amines.5
High reaction temperature and boring purification steps
were frequently demanded in this method. Pd-catalyzed
Buchwald–Hartwig amination reaction was demonstrated to
be a suitable alternative approach to 1-aminonaphthalene
derivatives from 1-halonaphthalene derivatives.6 However,
Recently, we developed Rh-catalyzed denitrogenative
cyclization of (E)-ethyl 2-(1-alkyl and arylsulfonyl-1H-1,-
2,3-triazol-4-yl)-3-arylacrylate obtained from ethyl (E)-
α-ethynyl-β-aryl-α,β-unsaturated esters and N-sulfonyl
azides with a copper(I) catalyst for the synthesis of a vari-
ety of functionalized benzofulvenes (Scheme 1, Eq. 1).7 In
addition, the synthesis of benzofulvenes was proved as a
one-pot method through tandem Cu(I)-catalyzed [3 + 2]
cycloaddition followed by Rh(II)-catalyzed denitrogenative
Scheme 1. Intramolecular cyclization of ethyl (E)-α-ethynyl-
β-aryl-α,β-unsaturated esters.
Figure 1. Bioactive 1-aminonaphthalene derivatives.
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Table 1. Reaction optimization.a
cyclization from ethyl (E)-α-ethynyl-β-aryl-α,β-unsaturated
esters and N-sulfonyl azides (Eq. 2).7 Moreover, a Cu(I)-
catalyzed 1,3-dipolar cycloaddition followed by ring-chain
isomerization to ketenimine formation tandem process was
reported by Chang et al. (Eq. 3).8 Taking the progress of
Rh(II)-catalyzed denitrogenative cyclization and Cu(I)-
catalyzed ketenimine formation in mind, we envisaged that
ethyl 4-(alkyl or aryl)sulfonamido-2-naphthoate (3) could
be synthesized through a tandem reaction of ethyl (E)-
α-ethynyl-β-aryl-α,β-unsaturated esters (1) with N-sulfonyl
azides (2). Furthermore, the sulfonamide skeleton is fre-
quently utilized in the design of bioactive compounds.9
Many drugs bearing N-arylsulfonamides are in clinical use
as HIV-1 protease inhibitors,10 non-nucleotide reverse tran-
scriptase inhibitors,11 anti-bacterials,12 and antitumor
agents.13 Herein, we develop a very practical method to
synthesize ethyl 4-(alkyl or arylsulfonamido)-2-naphthoates
from ethyl (E)-α-ethynyl-β-aryl-α,β-unsaturated esters (1)
in one step, in which a Cu(I)-catalyzed 1,3-dipolar cycload-
dition, ketenimine formation, and 6π-electrocyclization
followed by [1,3]-H shift tandem reaction took
place (Eq. 4).
Entry Cat.
Base
Solvent
Time (h) Yield (%)b
1
2
3
4
5
6
7
8
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
K2CO3
Na2CO3
Pyridine
Et3N
THF
THF
THF
THF
THF
12
12
5
0
0
22
3
10
DIPEA
3
3
3
28
2,6-lutidine THF
2,6-lutidine DCE
2,6-lutidine CH3CN
2,6-lutidine Toluene
80 (74)c
40
3
26
9
3
24
10
11
CuBr 2,6-lutidine THF
CuCl 2,6-lutidine THF
3
30
3
28
a Reactions were carried out with (E)-ethyl 2-ethynylcinnamate 1a
(0.2 mmol, 1.0 equiv), 4-methylbenzenesulfonyl azide 2a (2.0
equiv), CuI (10.0 mol%), and base (1.5 equiv) in solvent (1.0 mL,
0.2 M) at 60 ꢀC.
b NMR yield using dibromomethane as an internal standard.
c Isolated yield.
Results and Discussion
Ethyl (E)-α-ethynyl-β-aryl-α,β-unsaturated esters were pre-
pared in good to excellent yields from treatment of a vari-
ety of allenyl acetates, which were prepared from the
reaction of aldehydes with organoindium reagent in situ
generated from ethyl 4-bromobutynoate and indium in the
presence of lithium iodide in DMF and subsequent acetyla-
tion, with 10.0 mol % DABCO in DMF at room tempera-
ture (Scheme 2).14
80% yield (entries 4, 5, and 6). Further examination of the
solvents indicated that tetrahydrofuran (THF) was the opti-
mum solvent, and the other solvents, such as dichloroeth-
ane, acetonitrile, and toluene, gave inferior results (entries
6–9). Based on these results, CuBr and CuCl in the pres-
ence of 2,6-lutidine in THF were examined to determine
that CuI (10.0 mol%) was the best catalyst (entries 6, 10,
and 11).
With these optimized reaction conditions, we first exam-
ined the substrate scope of N-sulfonyl azides (Table 2).
Variation of the sulfonyl group in the N-sulfonyl azides (2)
slightly affected the efficiency of the reaction. When N-
methanesulfonyl azide was used, the desired product, ethyl
4-(methylsulfonamido)-2-naphthoate (3b), was obtained in
56% yield. N-4-methoxybenzenesulfonyl azide was treated
with 1a under the optimum reaction conditions, the desired
cyclized product (3c) was obtained in 80% yield with the
release of molecular nitrogen. N-4-chlorosulfonyl and
4-trifluoromethylsulfonyl azide were reacted with ethyl
2-ethynylcinnamate (1a) to produce the corresponding
naphthalene derivatives 3d and 3e in 58% and 60% yields,
respectively.
First, we investigated the reaction of ethyl
2-ethynylcinnamate (1a) with N-tosyl azide (2a) using a
variety of Cu catalysts (10.0 mol%), bases (1.5 equiv), and
solvents (Table 1). Potassium and sodium carbonate in the
presence of CuI were not effective in tetrahydrofuran
ꢀ
(THF) at 60 C for 12 h (entries 1 and 2). When pyridine
was used, the cyclized product, ethyl 4-((4-methylphenyl)
sulfonamido)-2-naphthoate (3a), was obtained in 22% yield
with the release of molecular nitrogen (entry 3). A variety
of bases, such as triethylamine, diisopropylethylamine, and
2,6-lutidine, in THF were screened to reveal that
2,6-lutidine was the best performing base, providing 3a in
Next, the substrate scope of ethyl (E)-α-ethynyl-β-aryl-α,-
β-unsaturated esters (1) were investigated. Electronic modifi-
cation of the substituents on the aryl group of ethyl (E)-
α-ethynyl-β-aryl-α,β-unsaturated esters (1) slightly influenced
the reaction efficiency. An electron-donating 2-methyl group
provided the desired naphthalene derivative 3f in 77% yield.
Meta-methyl-substituted substrate underwent the Cu(I)-
catalyzed cyclization reaction at the sterically less hindered
Scheme 2. Preparation of ethyl (E)-α-ethynyl-β-aryl-α,-
β-unsaturated esters.
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Cu-catalyzed Cyclization
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Table 2. Substrate scope of ethyl
(E)-α-ethynyl-β-aryl-α,β-unsaturated esters and N-sulfonyl azides.a
Scheme 3. Nitration and C H activation using ethyl
4-((4-methylphenyl)sulfonamido)-2-naphthoate.
Gratifyingly, the Cu(I)-catalyzed denitrogenative cyclization
reaction using furan-2-yl- and thiophen-2-yl-substituted sub-
strates took place to provide 3p and 3q in 48% and 60%
yields, respectively.
Next, we investigated the synthetic application of ethyl
4-((4-methylphenyl)sulfonamido)-2-naphthoate (3a) on
nitration and C H activation (Scheme 3). When 3a was
treated with sodium nitrate and oxone in nitromethane at 50
ꢀC for 3 h, the nitrated naphthalene derivative 4 was
obtained in 53% yield.15 Additionally, the Rh-catalyzed
C H activation reaction of 3a with ethyl acrylate in the
presence of Cu(OAc)2 in DMF at 100 ꢀC for 16 h produced
the isoindole 5 in 90% yield through the alkenylation
followed by Michael addition.16 The Ir-catalyzed
alkenylation of 3a with 3-hexyne in the presence of tri(teꢀrt-
butyl)phosphine and sodium carbonate in toluene at 135 C
for 2 h was successful and produced 6 in 80% yield.17
The possible mechanism for this cyclization reaction is
described in Scheme 4. As reported by Chang and
Wang,8,18 the reactive ketenimine B would be generated by
the ring-opening rearrangement of triazole intermediate A,
which was formed from alkyne 1 and N-sulfonyl azide 2 in
the presence of CuI and 2,6-lutidine. Subsequently the
a Reactions were carried out with 1 (0.2 mmol, 1.0 equiv), 2 (2.0
equiv), CuI (10.0 mol%), and 2,6-lutidine (1.5 equiv) in THF
(1.0 mL, 0.2 M) at 60 ꢀC for 3 h.
site to provide predominantly naphthalene derivative 3g.
These results indicate that the cyclization was influenced by
the steric effect rather than an electronic one. Exposure of
para-methyl- and methoxy-substituted substrate to a CuI cat-
alyst provided naphthalene derivatives 3i and 3j in 72% and
65% yields. The ethyl (E)-α-ethynyl-β-aryl-α,β-unsaturated
esters having 3,5-dimethoxy groups are good substrate for
the present transformation, producing 3k in 95% yield. Sub-
strates bearing electron-withdrawing chloride and bromide
groups underwent the Cu(I)-catalyzed cyclization reaction,
leading to the formation of naphthalene derivatives in moder-
ate yields. Regioselective formation of 3m from meta-bromo-
substituted substrate indicates that the cyclization was largely
effected by the steric effect. Acetoxy-substituted substrate
turned out to be compatible with the optimized conditions,
providing the corresponding product 3n in 50% yield. The
2-naphthyl-substituted substrate was selectively cyclized to
produce sterically less hindered anthracene derivative 3o.
Scheme 4. A plausible mechanism.
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intramolecular 6π-electrocyclization occurred and provided
the intermediate C. The following [1,3]-H shift and
protodecupration produced the final product, ethyl 4-(alkyl
or arylsulfonamido)-2-naphthoate 3, with regeneration of
the copper(I) catalyst.
7.74–7.70 (m, 1H), 7.64–7.61 (m, 1H), 7.20 (s, 1H), 4.46
(q, J = 7.1 Hz, 2H), 3.10 (s, 3H), 1.45 (t, J = 7.1 Hz, 3H);
13C NMR (100 MHz, CDCl3) δ 166.0, 133.6, 131.9, 131.2,
130.4, 130.2, 129.4, 127.8, 127.4, 122.0, 121.9, 61.7, 40.1,
14.4; IR (film) 3263, 1715, 1400, 1629, 775, cm−1; HRMS
(EI) m/z: [M]+ calcd for C14H15NO4S: 293.0722; found:
293.0721.
Experimental
Ethyl
4-(4-methoxyphenylsulfonamido)-2-naphthoate
General. Commercial available reagents were used with-
out purification. All reaction mixtures were stirred magneti-
cally and were monitored by thin-layer chromatography
using silica gel pre-coated glass plates, which were visual-
ized with UV light and then, developed using either iodine
or a solution of anisaldehyde. Flash column chromatogra-
(3c). Yield: 62 mg (80%); Rf = 0.3 (EtOAc:hexane = 1:2);
yellow solid, melting point: 152–153 ꢀC; 1H NMR
(400 MHz, CDCl3) δ 8.46 (s, 1H), 7.99 (d, J = 8.3 Hz,
1H), 7.93–7.90 (m, 1H), 7.86 (d, J = 1.5 Hz, 1H), 7.71 (dt,
J = 9.9, 2.5 Hz, 2H), 7.58–7.50 (m, 2H), 7.24 (s, 1H), 6.84
(dt, J = 9.9, 2.5 Hz, 2H), 4.40 (q, J = 7.1 Hz, 2H), 3.79 (s,
3H), 1.41 (t, J = 7.1 Hz, 3H); 13C NMR (100 MHz, CDCl3)
δ 166.0, 163.2, 133.4, 132.1, 131.1, 130.6, 129.9, 129.8,
129.6, 128.9, 127.5, 127.1, 122.0, 121.7, 114.2, 61.3, 55.6,
14.3; IR (film) 3258, 1716, 1628, 1348, 732 cm−1; HRMS
(EI) m/z: [M]+ calcd for C20H19NO5S: 385.0984; found:
385.0982.
1
phy was carried out using silica gel (230–400 mesh). H
NMR (400 MHz) and 13C{1H} NMR (100 MHz) spectra
were recorded on NMR spectrometer. Deuterated chloro-
form was used as the solvent and chemical shift values (δ)
are reported in parts per million relative to the residual sig-
1
nals of this solvent [δ 7.26 for H (chloroform‑d) and δ
77.2 for 13C{1H} (chloroform‑d). Infrared spectra were
recorded on FT-IR spectrometer as either a thin film
pressed between two sodium chloride plates or as a solid
suspended in a potassium bromide disk. High resolution
mass spectra (HRMS) were obtained by electron impact
(EI) ionization technique (magnetic sector—electric sector
double focusing mass analyzer) from the KBSI (Korea
Basic Science Institute Daegu Center). Melting points were
determined in open capillary tube.
Ethyl 4-(4-chlorophenylsulfonamido)-2-naphthoate (3d).
Yield: 45 mg (58%); Rf = 0.3 (EtOAc:hexane = 1:2); yel-
1
ꢀ
low solid, melting point: 147–149 C; H NMR (400 MHz,
CDCl3) δ 8.50 (d, J = 1.2 Hz, 1H), 7.96–7.93 (m, 2H),
7.83 (d, J = 1.4 Hz, 1H), 7.71 (dt, J = 9.2, 2.2 Hz, 2H),
7.60–7.53 (m, 2H), 7.37 (dt, J = 9.2, 2.2 Hz, 2H), 7.12 (s,
1H), 4.40 (q, J = 7.1 Hz, 2H), 1.42 (t, J = 7.1 Hz, 3H); 13C
NMR (100 MHz, CDCl3) δ 165.8, 139.7, 137.5, 133.5,
131.4, 131.3, 130.5, 130.0, 129.4, 129.2, 128.9, 127.5,
127.3, 122.5, 121.9, 61.5, 14.3; IR (film) 3257, 1718,
1628, 1376, 774, 737 cm−1; HRMS (EI) m/z: [M]+ Calcd
for C19H16ClNO4S: 389.0489; found: 389.0488.
Synthetic Procedure of Ethyl 4-(4-methylphenylsulfon-
amido)-2-naphthoate (3a).
A mixture of (E)-ethyl
2-ethynylcinnamate 1a (0.2 mmol, 40.0 mg, 1.0 equiv),
4-methylbenzenesulfonyl azide 2a (0.4 mmol, 78.9 mg, 2.0
equiv), CuI (3.8 mg, 10.0 mol%), and 2,6-lutidine
Ethyl
4-(4-(trifluoromethyl)phenylsulfonamido)-
2-naphthoate (3e). Yield: 51 mg (60%); Rf = 0.3 (EtOAc:
1
ꢀ
ꢀ
(32.1 mg, 1.5 equiv) was stirred in THF (1.0 mL) at 60 C
hexane = 1:2); yellow solid, melting point: 170–171 C; H
NMR (400 MHz, CDCl3) δ 8.53 (s, 1H), 7.97–7.95 (m,
1H), 7.89 (d, J = 8.1 Hz, 3H), 7.81 (d, J = 1.4 Hz, 1H),
7.67 (d, J = 8.3 Hz, 2H), 7.58–7.54 (m, 2H), 6.97 (s, 1H),
4.40 (q, J = 7.1 Hz, 2H), 1.40 (t, J = 7.1 Hz, 3H); 13C
NMR (100 MHz, CDCl3) δ 165.7, 142.6, 134.8 (q,
JCF = 33.0 Hz), 133.5, 131.5, 131.1, 130.8, 130.0, 129.2,
128.0, 127.6, 127.4, 126.2 (q, JCF = 3.7 Hz), 123.0, 121.7,
61.5, 14.3; IR (film) 3255, 1718, 1629, 1404, 1370,
775 cm−1; HRMS (EI) m/z: [M]+ calcd for C20H16F3NO4S:
423.0752; found: 423.0754.
for 3 h under N2. After cooling to room temperature and
evaporation of the solvents in vacuo, the crude product was
purified by column chromatography on silica gel using
EtOAc:hexane = 1:2. The desired product was obtained in
74% (34.9 mg) yield.
Ethyl 4-(4-methylphenylsulfonamido)-2-naphthoate (3a).
Yield: 34.9 mg (74%); Rf = 0.2 (EtOAc:hexane = 1:2); yel-
1
ꢀ
low solid, melting point: 156–158 C; H NMR (400 MHz,
CDCl3) δ 8.48 (s, 1H), 7.95–7.92 (m, 2H), 7.84 (d,
J = 1.4 Hz, 1H), 7.67 (dt, J = 9.0, 2.0 Hz, 2H), 7.59–7.52
(m, 2H), 7.20 (d, J = 7.1 Hz, 2H), 6.69 (s, 1H), 4.40 (q,
J = 7.1 Hz, 2H), 2.36 (s, 3H), 1.41 (t, J = 7.1 Hz, 3H); 13C
NMR (100 MHz, CDCl3) δ 165.9, 144.0, 136.1, 133.4,
131.9, 131.2, 130.0, 129.9, 129.7, 129.0, 127.5, 127.5,
127.2, 121.9, 61.3, 21.6, 14.3; IR (film) 3255, 1717, 1460,
Ethyl
4-(4-methoxyphenylsulfonamido)-8-methyl-
2-naphthoate (3f). Yield: 61.5 mg (77%); Rf = 0.2
(EtOAc:hexane = 1:2); yellow solid, melting point:
1
ꢀ
175–177 C; H NMR (400 MHz, CDCl3) δ 8.66 (s, 1H),
7.88 (d, J = 1.4 Hz, 1H), 7.77 (d, J = 8.5 Hz, 1H), 7.70 (dt,
J = 9.9, 2.5 Hz, 2H), 7.45 (dd, J = 8.4, 7.1 Hz, 1H), 7.37
(d, J = 7.0 Hz, 1H), 6.85 (dt, J = 9.9, 2.5 Hz, 2H), 6.77 (s,
1H), 4.41 (q, J = 7.1 Hz, 2H), 3.80 (s, 3H), 2.74 (s, 3H),
1.42 (t, J = 7.1 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ
166.2, 163.2, 136.7, 132.8, 132.3, 131.4, 130.7, 129.6,
128.6, 127.9, 127.1, 126.1, 121.7, 120.0, 114.2, 61.3, 55.6,
;
1400, 780 cm−1 HRMS (EI) m/z: [M]+ calcd for
C20H19NO4S: 369.1035; Found: 369.1039.
Ethyl 4-(methylsulfonamido)-2-naphthoate (3b). Yield:
33 mg (56%); Rf = 0.3 (EtOAc:hexane = 1:2); yellow solid,
1
ꢀ
melting point: 142–144 C; H NMR (400 MHz, CDCl3) δ
8.56 (s, 1H), 8.19–8.16 (m, 2H), 8.02 (d, J = 8.1 Hz, 1H),
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Cu-catalyzed Cyclization
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19.8, 14.3; IR (film) 3246, 1713, 1619, 1374, 772 cm−1
;
Ethyl 5,7-dimethoxy-4-(4-methoxyphenylsulfonamido)-
2-naphthoate (3k). Yield: 81.9 mg (95%); Rf = 0.2
(EtOAc:hexane = 1:2); yellow solid, melting point:
HRMS (EI) m/z: [M]+ calcd for C21H21NO5S: 399.1140;
found: 399.1139.
1
ꢀ
171–173 C; H NMR (400 MHz, CDCl3) δ 9.65 (s, 1H),
8.07 (d, J = 1.5 Hz, 1H), 7.94 (d, J = 1.6 Hz, 1H), 7.74 (dt,
J = 9.9, 2.5 Hz, 2H), 6.81 (dt, J = 9.9, 2.6 Hz, 2H), 6.76
(d, J = 2.3 Hz, 1H), 6.52 (d, J = 2.3 Hz, 1H), 4.40 (q,
J = 7.1 Hz, 2H), 3.97 (s, 3H), 3.87 (s, 3H), 3.76 (s, 3H),
1.43 (t, J = 7.1 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ
166.1, 163.0, 158.0, 156.6, 136.5, 134.6, 130.8, 129.6,
128.8, 125.4, 114.4, 113.9, 113.5, 101.2, 101.0, 61.2, 56.4,
55.5, 55.4, 14.4; IR (film) 3293, 1714, 1626, 1383,
768 cm−1; HRMS (EI) m/z: [M]+ calcd for C22H23NO7S:
445.1195; found: 445.1192.
Ethyl
2-naphthoate
4-(4-methoxyphenylsulfonamido)-7-methyl-
(3g) and Ethyl 4-(4-methoxy-
phenylsulfonamido)-5-methyl-2-naphthoate (3h). Yield:
70.2 mg (88%); Rf = 0.2 (EtOAc:hexane = 1:2); yellow
1
solid, melting point: 167–168 ꢀC; data for the major H
NMR (400 MHz, CDCl3) δ 8.36 (s, 1H), 7.89 (d,
J = 8.7 Hz, 1H), 7.79–7.76 (m, 1H), 7.70 (dt, J = 9.9,
2.5 Hz, 2H), 7.67 (s, 1H), 7.41–7.36 (m, 1H), 7.15 (s, 1H),
6.84 (dt, J = 9.9, 2.5 Hz, 2H), 4.38 (q, J = 7.1 Hz, 2H),
3.79 (s, 3H), 2.49 (s, 3H), 1.40 (t, J = 7.1 Hz, 3H); data for
the minor 1H NMR (400 MHz, CDCl3) δ 8.44 (d,
J = 1.8 Hz, 1H), 7.79–7.76 (m, 1H), 7.64 (dt, J = 9.7,
2.5 Hz, 2H), 7.48 (d, J = 1.7 Hz, 1H), 7.41–7.36 (m, 2H),
6.98 (s, 1H), 6.89 (dt, J = 9.8, 2.5 Hz, 2H), 4.34 (q,
J = 7.1 Hz, 2H), 3.83 (s, 3H), 3.01 (s, 3H), 1.36 (t,
J = 7.1 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 166.15,
165.72, 163.18, 163.10, 137.05, 135.17, 133.74, 133.68,
133.08, 132.69, 131.98, 131.94, 131.71, 131.22, 130.91,
130.61, 129.81, 129.63, 129.42, 129.22, 129.05, 128.79,
127.47, 126.72, 126.47, 124.81, 121.87, 120.80, 114.18,
114.15, 61.26, 61.20, 55.60, 55.58, 25.28, 21.47, 14.32,
14.24; IR (film) 3253, 1716, 1596, 1371, 774 cm−1; HRMS
(EI) m/z: [M]+ calcd for C21H21NO5S: 399.1140; found:
399.1143.
Ethyl
2-naphthoate (3l).
6-chloro-4-(4-methoxyphenylsulfonamido)-
Yield: 46.1 mg (55%); Rf = 0.2
(EtOAc:hexane = 1:2); yellow solid, melting point:
1
ꢀ
174–176 C; H NMR (400 MHz, CDCl3) δ 8.46 (s, 1H),
7.89–7.83 (m, 3H), 7.69 (dt, J = 9.9, 2.5 Hz, 2H), 7.47 (dd,
J = 8.7, 2.0 Hz, 1H), 6.89 (dt, 2H), 6.71 (s, 1H), 4.40 (q,
J = 7.1 Hz, 2H), 3.83 (s, 3H), 1.41 (t, J = 7.1 Hz, 3H); 13C
NMR (100 MHz, CDCl3) δ 165.6, 163.4, 135.4, 132.5,
131.7, 131.3, 131.3, 130.4, 130.0, 129.7, 128.2, 127.9,
124.1, 121.7, 114.3, 61.5, 55.6, 14.3; IR (film) 3249, 1718,
1624, 1376, 763, 731 cm−1; HRMS (EI) m/z: [M]+ calcd
for C20H18ClNO5S: 419.0594; found: 419.0598.
Ethyl
7-bromo-4-(4-methoxyphenylsulfonamido)-
2-naphthoate (3m). Yield: 46.5 mg (50%); Rf = 0.3
Ethyl
2-naphthoate (3i).
4-(4-methoxyphenylsulfonamido)-6-methyl-
Yield: 57.5 mg (72%); Rf = 0.3
(EtOAc:hexane = 1:2); yellow solid, melting point:
1
ꢀ
179–181 C; H NMR (400 MHz, CDCl3) δ 8.38 (s, 1H),
8.09 (d, J = 1.8 Hz, 1H), 7.90 (d, J = 9.0 Hz, 1H), 7.76 (d,
J = 1.2 Hz, 1H), 7.69–7.63 (m, 3H), 6.88 (dt, J = 9.9,
2.4 Hz, 2H), 6.78 (s, 1H), 4.40 (q, J = 7.1 Hz, 2H), 3.82 (s,
3H), 1.41 (t, J = 7.1 Hz, 3H); 13C NMR (100 MHz, CDCl3)
δ 165.5, 163.4, 134.6, 132.4, 132.2, 131.6, 130.2, 130.2,
129.7, 129.0, 128.7, 124.2, 122.7, 121.5, 114.3, 61.5, 55.6,
(EtOAc:hexane = 1:2); yellow solid, melting point:
1
ꢀ
171–173 C; H NMR (400 MHz, CDCl3) δ 8.42 (s, 1H),
7.81 (d, J = 8.1 Hz, 2H), 7.72 (dt, J = 9.9, 2.5 Hz, 2H),
7.68 (d, J = 0.5 Hz, 1H), 7.35 (dd, J = 8.4, 1.4 Hz, 1H),
6.90 (s, 1H), 6.86 (dt, J = 9.9, 2.6 Hz, 2H), 4.39 (q,
J = 7.1 Hz, 2H), 3.80 (s, 3H), 2.47 (s, 3H), 1.40 (t,
J = 7.1 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 166.1,
163.2, 139.4, 131.7, 131.4, 131.3, 130.7, 129.8, 129.7,
129.4, 126.6, 122.2, 121.1, 114.1, 61.2, 55.6, 22.2, 14.3;
IR (film) 3249, 1715, 1630, 1378, 763 cm−1; HRMS
(EI) m/z: [M]+ calcd for C21H21NO5S: 399.1140; found:
399.1139.
14.3; IR (film) 3251, 1727, 1592, 1399, 811, 761 cm−1
;
HRMS (EI) m/z: [M]+ Calcd for C20H18BrNO5S: 463.0089
found: 463.0090.
Ethyl
6-acetoxy-4-(4-methoxyphenylsulfonamido)-
2-naphthoate (3n). Yield: 44.3 mg (50%); Rf = 0.3
(EtOAc:hexane = 1:2); yellow solid, melting point:
1
ꢀ
Ethyl
2-naphthoate (3j).
6-methoxy-4-(4-methoxyphenylsulfonamido)-
Yield: 54.1 mg (65%); Rf = 0.2
140–142 C; H NMR (400 MHz, CDCl3) δ 8.44 (s, 1H),
7.92 (d, J = 8.8 Hz, 1H), 7.76 (d, J = 1.3 Hz, 1H),
7.71–7.67 (m, 3H), 7.29 (dd, J = 8.8, 2.2 Hz, 1H), 6.89 (s,
1H), 6.86 (dt, J = 9.9, 2.5 Hz, 2H), 4.39 (q, J = 7.1 Hz,
2H), 3.81 (s, 3H), 2.36 (s, 3H), 1.41 (t, J = 7.1 Hz, 3H);
13C NMR (100 MHz, CDCl3) δ 169.3, 165.7, 163.3, 150.9,
132.6, 131.9, 131.4, 131.3, 130.5, 129.8, 129.7, 127.4,
123.3, 122.7, 114.2, 114.0, 61.4, 55.6, 21.1, 14.3; IR (film)
3250, 1716, 1632, 1371, 763 cm−1; HRMS (EI) m/z: [M]+
calcd for C22H21NO7S: 443.1039; found: 443.1041.
(EtOAc:hexane = 1:2); yellow solid, melting point:
1
ꢀ
172–175 C; H NMR (400 MHz, CDCl3) δ 8.40 (s, 1H),
7.81 (d, J = 9.0 Hz, 1H), 7.78 (d, J = 1.4 Hz, 1H), 7.71 (dt,
J = 9.9, 2.5 Hz, 2H), 7.29 (d, J = 2.3 Hz, 1H), 7.16 (dd,
J = 8.9, 2.4 Hz, 1H), 7.04 (s, 1H), 6.86 (dt, J = 10.0,
2.5 Hz, 2H), 4.38 (q, J = 7.1 Hz, 2H), 3.87 (s, 3H), 3.81 (s,
3H), 1.40 (t, J = 7.1 Hz, 3H); 13C NMR (100 MHz, CDCl3)
δ 166.1, 163.2, 160.3, 133.5, 131.4, 130.7, 130.0, 129.6,
128.8, 125.1, 123.6, 120.2, 114.2, 100.8, 61.1, 55.6, 55.7,
14.3; IR (film) 3258, 1714, 1626, 1380, 766 cm−1; HRMS
(EI) m/z: [M]+ Calcd for C21H21NO6S: 415.1090; found:
415.1092.
Ethyl
4-(4-methoxyphenylsulfonamido)anthracene-
2-carboxylate (3o). Yield: 64.4 mg (74%); Rf = 0.4
(EtOAc:hexane = 1:2); yellow solid, melting point:
1
ꢀ
195–196 C; H NMR (400 MHz, CDCl3) δ 9.69–9.65 (m,
Bull. Korean Chem. Soc. 2019
© 2019 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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5

BULLETIN OF THE
Article
Cu-catalyzed Cyclization
KOREAN CHEMICAL SOCIETY
1H), 8.45 (d, J = 1.8 Hz, 1H), 7.90–7.86 (m, 1H),
7.77–7.70 (m, 3H), 7.67–7.62 (m, 4H), 6.88–6.83 (m, 3H),
4.38 (q, J = 7.1 Hz, 2H), 3.81 (s, 3H), 1.40 (t, J = 7.1 Hz,
3H); 13C NMR (100 MHz, CDCl3) δ 165.6, 163.3, 134.1,
134.1, 133.3, 130.5, 130.2, 129.9, 129.6, 129.1, 129.0,
128.9, 127.9, 127.5, 127.3, 127.3, 126.8, 126.2, 114.1,
61.3, 55.6, 14.3; IR (film) 3250, 1715, 1594, 1375,
767 cm−1; HRMS (EI) m/z: [M]+ calcd for C24H21NO5S:
435.1140 found: 435.1141.
Synthetic Procedure of Ethyl 2-(2-ethoxy-2-oxoethyl)-
1-tosyl-1,2-dihydrobenzo[cd]indole-7-carboxylate (5). A
Schlenk tube was charged with Cu(OAc)2 (76.3 mg, 2.1
equiv), [Cp*RhCl2]2 (3.1 mg, 2.5 mol%), and ethyl
4-(4-methylphenylsulfonamido)-2-naphthoate 3a (0.2 mmol,
73.9 mg, 1.0 equiv). After purged with nitrogen, DMF
(0.4 mL) and ethyl acrylate (32.7 μL, 1.5 equiv) were
added. The mixture was stirred at 100 ꢀC for 16 h, followed
by dilution CH2Cl2 and filtration through celite. All vola-
tiles were removed under reduced pressure. The purification
was performed by flash column chromatography on silica
gel using EtOAc:hexane = 1:5. The desired product was
obtained in 90% (84.1 mg) yield.
Ethyl
4-(4-methoxyphenylsulfonamido)benzofuran-
6-carboxylate (3p). Yield: 36.0 mg (48%); Rf = 0.3
(EtOAc:hexane = 1:2); brown solid, melting point:
143–145 ꢀC; 1H NMR (400 MHz, CDCl3) δ 8.02 (t,
J = 1.1 Hz, 1H), 7.72 (dt, J = 10.1, 2.6 Hz, 2H), 7.70 (d,
J = 1.2 Hz, 1H), 7.69 (d, J = 2.2 Hz, 1H), 7.16 (s, 1H),
6.89 (dd, J = 2.3, 1.0 Hz, 1H), 6.87 (dt, J = 9.7, 2.4 Hz,
2H), 4.38 (q, J = 7.1 Hz, 2H), 3.81 (s, 3H), 1.40 (t,
J = 7.1 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 166.0,
163.3, 155.0, 147.8, 130.2, 129.6, 129.1, 127.3, 126.8,
117.9, 114.3, 111.0, 104.7, 61.3, 55.6, 14.3; IR (film)
3254, 1714, 1621, 1371, 1305, 769 cm−1; HRMS (EI) m/z:
[M]+ calcd for C18H17NO6S: 375.0777 found: 375.0775.
Ethyl 2-(2-ethoxy-2-oxoethyl)-1-tosyl-1,2-dihydrobenzo
[cd]indole-7-carboxylate (5). Yield: 84.1 mg (90%);
Rf = 0.3 (EtOAc:hexane = 1:5); white solid, melting point:
103–105 ꢀC; 1H NMR (400 MHz, CDCl3) δ 8.23 (d,
J = 0.8 Hz, 1H), 8.11 (d, J = 0.8 Hz, 1H), 7.75–7.70 (m,
3H), 7.50–7.46 (m, 1H), 7.31–7.30 (m, 1H), 7.17 (d,
J = 8.0 Hz, 2H), 5.73–5.59 (m, 1H), 4.51–4.42 (m, 2H),
4.24–4.19 (m, 2H), 3.65–3.59 (m,. 1H), 2.95–2.89 (m, 1H),
2.29 (s, 3H), 1.46 (t, J = 7.1 Hz, 3H), 1.24 (t, J = 7.1 Hz,
3H); 13C NMR (100 MHz, CDCl3) δ 170.5, 166.7, 144.7,
142.3, 138.8, 133.8, 131.4, 131.2, 130.2, 129.9, 129.2,
127.3, 125.4, 123.3, 120.2, 107.8, 65.1, 61.4, 60.9, 42.1,
21.5, 14.4, 14.1; IR (film) 3300, 1725, 1550, 1390, 1377,
Ethyl
4-(4-methoxyphenylsulfonamido)benzo[b]-thio-
phene-6-carboxylate (3q). Yield: 46.9 mg (60%); Rf = 0.3
(EtOAc:hexane = 1:2); brown solid, melting point:
178–179 ꢀC; 1H NMR (400 MHz, CDCl3) δ 8.41 (t,
J = 1.0 Hz, 1H), 7.82 (d, J = 1.3 Hz, 1H), 7.73 (dt, J = 9.9,
2.5 Hz, 2H), 7.59 (d, J = 5.6 Hz, 1H), 7.41 (dd, J = 5.6,
0.8 Hz, 1H), 7.26 (s, 1H), 6.86 (dt, J = 9.9, 2.5 Hz, 2H),
4.39 (q, J = 7.1 Hz, 2H), 3.80 (s, 3H), 1.41 (t, J = 7.1 Hz,
3H); 13C NMR (100 MHz, CDCl3) δ 166.0, 163.3, 140.7,
137.8, 130.8, 130.8, 130.3, 129.6, 127.1, 122.5, 120.4,
119.6, 114.3, 61.3, 55.6, 14.3; IR (film) 3263, 1713, 1595,
;
1280, 780 cm−1 HRMS (EI) m/z: [M]+ calcd for
C25H25NO6S: 467.1403; found: 467.1403.
Synthetic Procedure of Ethyl (E)-5-(hex-3-en-3-yl)-
4-((4-methylphenyl)sulfonamido)-2-naphthoate (6).
A
mixture of ethyl 4-(4-methylphenylsulfonamido)-
2-naphthoate 3a (0.2 mmol, 73.9 mg, 1.0 equiv), 3-hexyne
(22.7 μL, 1.0 equiv), [IrCl(cod)]2 (6.7 mg, 5.0 mol%), P(t-
Bu)3 (6.1 mg, 15.0 mol%), and Na2CO3 (10.6 mg, 0.5
1367, 772 cm−1
;
HRMS (EI): [M]+ calcd for
C18H17NO5S2: 391.0548 found: 391.0545.
ꢀ
equiv) was stirred in toluene (0.5 mL) at 135 C for 2 h
Synthetic Procedure of Ethyl 4-((4-methylphenyl)sul-
fonamido)-1-nitro-2-naphthoate (4). A mixture of ethyl
4-(4-methylphenylsulfonamido)-2-naphthoate 3a (0.2 mmol,
73.9 mg, 1.0 equiv), NaNO2 (27.6 mg, 2.0 equiv), and
oxone (60.9 mꢀg, 2.0 equiv) was stirred in nitromethane
(1.0 mL) at 50 C for 3 h under air. After the reaction was
concentrated, the residue was purified by flash column
chromatography using EtOAc:hexane = 1:5. The desired
product was obtained in 53% (43.9 mg) yield.
under nitrogen. After cooling to room temperature and
evaporation of the solvents in vacuo, the crude product was
purified by column chromatography on silica gel using
EtOAc:hexane = 1:6. The desired product was obtained in
80% (72.2 mg) yield.
Ethyl-5-(hex-3-en-3-yl)-4-((4-methylphenyl)sulfonamido)
-2-naphthoate (6).
Yield: 72.2 mg (80%); Rf = 0.3
(EtOAc:hexane = 1:6); brown solid, melting point:
1
ꢀ
Ethyl
2-naphthoate (4).
4-((4-methylphenyl)sulfonamido)-1-nitro-
Yield: 43.9 mg (53%); Rf = 0.3
104–106 C; H NMR (400 MHz, CDCl3) δ 9.11 (s, 1H),
8.24 (d, J = 1.6 Hz, 1H), 7.99 (d, J = 1.6 Hz, 1H),
7.83–7.78 (m, 3H), 7.43–7.39 (m, 1H), 7.24 (d, J = 8.0 Hz,
2H), 7.18–7.16 (m, 1H), 5.76–5.72 (m, 1H), 4.40 (q,
J = 7.1 Hz, 2H), 2.95–2.43 (m, 2H), 2.37–2.15(m, 2H),
2.35 (s, 3H), 1.43 (t, J = 7.1 Hz, 3H), 1.23 (t. J = 7.5 Hz,
3H), 0.89 (t, J = 7.5 Hz, 3H); 13C NMR (100 MHz, CDCl3)
δ 166.1, 144.0, 143.9, 138.4, 136.6, 134.7, 134.6, 134.4,
131.2, 129.8, 129.6, 127.7, 127.3, 127.0, 125.9, 123.9,
113.1, 61.2, 26.5, 21.6, 21.5, 14.4, 13.9, 12.2; IR (film)
3285, 1737, 1420, 1395, 795 cm−1; HRMS (EI) m/z: [M]+
Calcd for C26H29NO4S: 451.1817; found: 451.1817.
(EtOAc:hexane = 1:5); white solid, melting point: 154–156
ꢀC; 1H NMR (400 MHz, CDCl3) δ 8.04–8.01 (m, 1H),
7.90 (s, 1H), 7.76–7.73 (m, 3H), 7.68–7.73 (m, 3H), 7.54
(br, NH), 7.25 (d, J = 8.0 Hz, 2H), 4.40 (q, J = 7.1 Hz,
2H), 2.38 (s, 3H), 1.39 (t, J = 7.16 Hz, 3H); 13C NMR
(100 MHz, CDCl3) δ 162.7, 146.5, 144.8, 135.5, 133.9,
129.9, 129.6, 127.5, 125.0, 123.4, 121.8, 119.6, 119.1,
62.7, 21.6, 13.8; IR (film) 3210, 1690, 1440, 1397,
780 cm−1; HRMS (EI) m/z: [M]+ calcd for C20H18N2O6S:
414.4320; found: 414.4320.
Bull. Korean Chem. Soc. 2019
© 2019 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.bkcs.wiley-vch.de
6

BULLETIN OF THE
Article
Cu-catalyzed Cyclization
KOREAN CHEMICAL SOCIETY
G. Rombouts, L. Pieters, A. Haemers, R. A. Dommisse, Syn-
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Conclusion
In conclusion, we developed a Cu(I)-catalyzed cyclization
reaction of ethyl (E)-α-ethynyl-β-aryl-α,β-unsaturated esters
with N-sulfonyl azides in the presence of 2,6-lutidine in
ꢀ
THF at 60 C for 3 h. This method enabled efficient syn-
thesis of a wide range of 1-aminonaphthalene and
3-aminobenzofuran and 3-aminobenzothiophene derivatives
with the release of molecular nitrogen.
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Acknowledgments. This paper is dedicated to Professor
Hong-Seok Kim (Kyungpook National University) for his
honorable retirement. This work was supported by the
National Research Foundation of Korea (NRF) grant
funded by the Korea government (MSIP) (2011-0018355
and 2017R1A4A1015405) and by 2017 Research Grant
from Kangwon National University (No. 520170529).
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Supporting Information. Copies of 1H and 13C NMR
spectra for all products (PDF) is available in the online ver-
sion of this article.
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© 2019 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.bkcs.wiley-vch.de
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